1. Field of the Invention.
The field of the invention is fasteners, particularly fasteners employed on electrical apparatus such as relays, including contactors and motor starters, and more particularly on large electrical apparatus involving the connection of very large conductors.
2. Description of the Prior Art.
Fasteners are employed on electrical apparatus to provide secure connection between conductive elements, or contacts. For electrical power connections of approximately 30 amps or more, the threaded fastener has been the preferred method because it delivers a large, positive mechanical force over a wide contact area thus insuring a low resistance connection. When the connections to be made involve very large conductors, including bus bars, which are difficult or impossible to bend by hand, the connections are usually made with a bolt and nut through a stationary terminal. Alternatively, a threaded hole is sometimes formed in the stationary terminal itself to receive the bolt as in the terminal connection for the disconnect switch of U.S. Pat. No. 4,251,700.
As shown in U.S. Pat. No. 3,564,466, bus bar connections are used, for example, to interconnect physically adjacent devices together for such applications as motor reversing. Again, when very large bus bar conductors are used, it is desirable to have a terminal assembly which allows access to both the top and bottom sides of the stationary terminal so that the bus bar connections can be made on one side, for example the bottom side, such that they will not interfere with the other connections on the top side.
Additionally, the device to which the connections are being made is usually housed inside an enclosure for safety reasons, which limits accessability to the device. In order to provide for ease of assembly and maintenance under such conditions, it is beneficial to have the fasteners used for electrical connections held captive. Where captive parts are used, it is also desirable to be able to replace the captive part only, rather than having the captive part permanently bounded to the apparatus body.
While existing terminals for making such connections have been used for many years and are generally satisfactory, none offer all of the desirable features described above in a terminal for very large conductors, i.e. threaded fasteners for contact, access to both sides of a stationary terminal, and replaceable captive parts. If a threaded stationary terminal is used as in the terminal for the disconnect switch of U.S. Pat. No. 4,251,700 then connections can be made to only one side of the stationary terminal. If a bolt and nut are used through a hole in the stationary terminal, as is the prevailing practice in the industry, then connections could be made to both sides of the stationary terminal, but the nut is not held captive.